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zeeglen
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
zeeglen   3/1/2011 4:03:27 PM
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"[Simply stated, these limitations are: "Bandwidth and antenna size are inversely related" and "efficiency and antenna size are directly related." This means that in general, a larger antenna will have larger bandwidth and efficiency.]" This is a bit confusing, if bandwidth is inversely related to antenna size, then a larger antenna would have a smaller bandwidth. The few times I made short antennas the bandwidth decreased as antenna length decreased. Am I missing something? Otherwise a very interesting and well-written article.

SkyCross CTO
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
SkyCross CTO   3/1/2011 9:14:15 PM
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You are not missing something, you are correct - Bandwidth and size are DIRECTLY related, not inversely related.

zeeglen
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
zeeglen   3/2/2011 11:41:27 AM
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Paul, thank you for clearing this up.

jwc
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
jwc   3/2/2011 3:39:51 PM
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Big often relates to narrow band but it doesn't always mean narrow band. For example log-periodic antennas are huge yet they cover enormous bandwidths. I'm sure there are many other examples.

JanineLove
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
JanineLove   3/2/2011 7:21:26 PM
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I fixed this in the article above.

zeeglen
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
zeeglen   3/3/2011 6:17:04 AM
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@JWC Good point. I was considering only single element with length reduction below 1/2 (dipole) and 1/4 (ground plane) wavelength. Next marketing breakthrough - a log periodic on a cellphone! (Just kidding)

sajid.bashir
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
sajid.bashir   3/3/2011 7:01:09 PM
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I am still confused. AS I know is the antenna size is directly related to wavelength so at higher frequencies we can have smaller antennas. The efficiency is directly related to size as it allows capturing more energy. If this is true then how does bandwith relate to antenna size?

Brakeshoe
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
Brakeshoe   3/3/2011 11:32:10 PM
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Remember, a modulated RF signal will have sidebands. Let's look at the simplest case of a broadcast AM radio (6A3, double sideband full carrier) signal operating with a carrier frequency f(c) of 600 kHz modulated at 100% with a 4.0 kHz sinusoid. We now have a signal that occupies the spectrum from 596 kHz to 604 kHz, and the Q of the output amp stage as well as the antenna must be low enough to not trim off the sidebands.

Brakeshoe
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re: Skycross: Antenna challenges in smartphones and tablets with 4G rising
Brakeshoe   3/3/2011 11:39:02 PM
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Note on second paragraph on second page: "The coupling magnitude is inversely proportional to the separation distance..." And is also reduced by the scalar dot product of the angular difference in polarization when linear polarization is used.



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